This invention relates to electronic systems for sensing dangerous conditions and actuating safety devices, and particularly to a crash-responsive air-bag detonator for motor vehicles.
Such systems may, for example, be composed of an acceleration sensor, a sensor-responsive evaluation circuit, and an output stage. In one such system, the evaluating circuit is composed of a threshold device which conducts only if the acceleration sensor output signal reaches or exceeds a predetermined magnitude, a preamplifier, an integrator, and a threshold switch. The precision of the entire sensor system depends specifically on the precision of the evaluating circuit components. Establishing a zero or null and a threshold value for these components requires different reference voltages. To avoid drift of the system entered data, these reference voltages and the differences between the individual reference voltages must be held stable.
As a further point, these known circuits involve starting difficulties unless additional auxilliary circuits are used. For example, resetting the integrator in the evaluating circuit, either during starting or during operation of the system, may create a signal which should not, but might, reach the output stage and actuate the safety device.
These known circuits also have the disadvantage of failing to indicate defects to the driver or indicate such defects only by means of complex auxilliary circuits.
An object of the invention is to avoid disadvantages of these systems.
Another object of the invention is to improve systems of this type.